I'm always on the search for the perfect white t-shirt... but the search may finally be over!! Everlane is a new fashion company out of SF that sells high end designer product at lower prices! I currently own one white v-neck and, admittedly, have at times worn it several days in a row :) It is seriously the best and if you love t-shirts like I do you should check it out!
p.s. it's a membership site - and I may have a few invites so let me know if you are truly interested!